The challenge to meet the ever increasing demand for oil has resulted in increasing activities in crude oil recovery from oil reservoirs for refinery processes and various other applications. These activities have resulted in contaminating various environments such as soil, groundwater, sand, drinking water, etc, with hydrocarbons. There are now two worldwide challenges that need to be met: 1) recovering the petroleum deposits for oil reservoirs; and 2) remediating the hydrocarbon-contaminated environmental sites.
Heavy crude oil in the form of petroleum deposits and oil reservoirs are distributed worldwide and because of its relatively high viscosity, it is essentially immobile and cannot be easily recovered by conventional primary and secondary means. Expanding efforts to develop alternative cost efficient oil recovery processes have been documented (Kianipey, S. A. and Donaldson, E. C. 61st Annual Technical Conference and Exhibition, New Orleans, La., USA, Oct. 5-8, 1986).
Microbial Enhanced Oil Recovery (MEOR) is a methodology for increasing oil recovery by the action of microorganisms (Brown, L. R., et al., SPE 59306, SPE/DOE Improved Oil Recovery Symposium, Oklahoma, Apr. 3-5, 2000). MEOR research and development is an ongoing effort directed at discovering techniques to use microorganisms to modify crude oil properties to benefit oil recovery (Sunde. E., et al., SPE 24204, SPE/DOE 8th Symposium on enhanced Oil Recovery, Tulsa, Okla., USA, Apr. 22-24, 1992). In MEOR processes, useful microbes are typically hydrocarbon-utilizing, non-pathogenic microorganisms, which use hydrocarbons as their source of energy to grow or excrete natural bio-products such as alcohols, gases, acids, surfactants and polymers. These bio-products change the physio/chemical properties of the crude oil and stimulate changes in the oil-water-rock interactions to improve oil recovery.
Remediation of hydrocarbon-contaminated sites is difficult due to the structural properties of the crude oil. Crude oil is characterized by apolar C—C and C—H bonds and lacks functional chemical groups that contribute to the crude oil's recalcitrant nature. Crude oil consists of alkanes, alkenes, alkynes, aromatic polycyclic hydrocarbons, asphaltenes and resins. Conventional methods used to remediate hydrocarbons include solvent treatment and polymeric particles having covalently bound to a polymeric component as described in U.S. Pat. No. 7,449,429B2, U.S. Pat. No. 6,852,234B2, U.S. Pat. No. 7,465,395, U.S. Pat. No. 7,201,804B2, U.S. Pat. No. 7,473,672B2, U.S. Pat. No. 7,442,313B2; site excavation as practiced by Ground Remediation Systems, LTD, UK; and pump and treat, which involves pumping out contaminated groundwater with the use of a submersible or vacuum pump The extracted groundwater is then purified by slowly proceeding through a series of vessels that contain materials designed to adsorb the contaminants from the groundwater and vacuum extraction (U.S. Pat. No. 7,172,688B2). These processes are costly, time consuming and leave undesirable environmental footprints.
Alternatively, microorganisms may be used for in situ bioremediation of hydrocarbon-contaminated sites. For example, biodegradation of contaminants by indigenous microbial populations is common in many aerobic environments (Gibson, D. T., Microbial Degradation of Organic Compounds, 1984, Marcel Dekker, NY). Addition of oxygen and nutrients to stimulate the growth of indigenous microorganisms can be an effective bioremediation tool in the cleanup of crude oil spill. An alternative approach, reported for soils contaminated with crude oil or petroleum hydrocarbons, is the introduction into the soils of microbes capable of degrading these chemicals. These processes rely on oxidative degradation under aerobic conditions, and the microbes use the hydrocarbon contaminant as the carbon and energy source (U.S. Pat. No. 6,652,752B2). However, in many cases aerobic bioremediation is impractical because of the anoxic nature of the natural environments of the hydrocarbon-contaminated sites, such as soil, groundwater aquifers, fresh water and marine sediments and oil reservoirs.
Since application of microorganisms for MEOR and in-situ bioremediation is a promising alternative to traditional oil recovery or in situ remediation means, developing methods for identifying microorganisms useful in these processes, which would allow cost-effective processes for MEOR and bioremediation, is important. Previously described methods for such applications, for example, include obtaining the sample under specific conditions with a defined nutrient medium in the presence of anaerobic gas mixtures (U.S. Patent Application No. 2007/0092930A1). A process for stimulating the in situ activity of a microbial consortium to produce methane for oil was described (U.S. Pat. No. 6,543,535B2). However, such processes are time consuming, labor-intensive and therefore costly.
Thus, there is a need for developing methods to: 1) obtain a steady state population of consortium of microorganisms that can grow in or on oil under anaerobic denitrifying conditions; 2) identify the members of the steady state consortium for properties that might be useful in oil modification and/or degradation and 3) use said steady state consortium of microorganisms, in a cost-effective way, for enhanced oil recovery from wells or reservoirs or in situ bioremediation of hydrocarbon-contaminated sites.